Atomic Models

John Dalton

Nov 3, 1803

proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together.

Dmitri Mendeleev

Nov 3, 1869

Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". and that is now known as the "Periodic table"

James clerk maxewell

Nov 4, 1873

put forward the theory of electromagnetism and made the connection between light and electromagnetic waves

Sir William Crookes

Nov 5, 1879

Discovered cathode rays had these properties:
1. travel in straight lines from the cathode
2. causes glass to fluoresce
3. impart a negative charge to objects they strike
4. are deflected by electric fields and magnets to suggest a negative charge

Frederick Soddy

Nov 5, 1900

Came up with the term "isotope" to explain the unintentional breakdown of radioactive elements.

Rutherford

Nov 5, 1901

described the atom as a tiny, dense, positively charged core called a nucleus

Hans Geiger

Nov 5, 1906

German physicist who introduced the first successful detector (the Geiger counter) of individual alpha particles and other ionizing radiations

Niels Bohr

Nov 5, 1922

proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.

Schrodinger

Nov 5, 1930

Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom

Modern day theory

Nov 5, 2012

Present-day atomic theory is largely based on concepts proposed in the 1920's by the Austrian Erwin Schrdinger, the Germans Werner Heisenberg and Max Born, Paul Dirac of Great Britain, and Louis de Broglie of France